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Mike V.
Mike V., Nissan Technician
Category: Nissan
Satisfied Customers: 25184
Experience:  Nissan factory trained and Certified Subaru Technician.
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I have a Nissan sentra, motor runs good sometimes and then

Customer Question

I have a Nissan sentra, motor runs good sometimes and then when you switch it off it will not crank back up it just keeps turning. We have checked the Cam sensor, 02 Sensor, Mass Air Flow Sensor, and Crank Sensor, It started one time and we thought it was fixed and drove it 200 miles whichenvolved starting and stopping several times and getting gas in it, it even sat for a few hours before we started it. We got home with the car turned it off overnight and the next morning it would not crank again. We checked over the car again could not figure it out so we carried it to the Nissan dealership and they said it was the crank sensor and computer because they said was bad computer said not communicating. We went and got a used matching computer they put that in and called and said it was ready and when we got there to pick it up it would not start again so that did not fix the problem that it was communicating now but still will not crank they said they could pull crank sensor and it will crank up, but not rev up. They called another Nissan tech he said pull valve cover and check said it was way out of time that chain was stretched, This car only has 67k miles on it with no rattle noise of any kind when it is running, I asked how it could run then and not run I do not think that this is a chain issue I think that it is more of a wiring problem. We are stumped! What are your thoughts?Thanks
Submitted: 1 year ago.
Category: Nissan
Expert:  Mike V. replied 1 year ago.

Hi there,

What year is this car? Engine size?

Customer: replied 1 year ago.
IT IS A 2006 NISSAN SENTRA WITH A 1.8
Expert:  Mike V. replied 1 year ago.

Do you have the car with you now and will it start or not?

Customer: replied 1 year ago.
I HAVE THE CAR HERE AND NO IT WILL NOT RUN
Expert:  Mike V. replied 1 year ago.

OK

FIRST I DON'T THINK IT'S A TIMING CHAIN ISSUE EITHER. THAT WOULD BE PRETTY CONSISTENT IN MY OPINION.

WHEN YOU TURN THE KEY ON, DOES THE SERVICE ENGINE SOON LIGHT COME ON?

Customer: replied 1 year ago.
WHEN THE KEY IS TURNED ON THE SERVICE ENGINE SOON LIGHT COMES ON
Expert:  Mike V. replied 1 year ago.

OK

DO YOU HAVE A COMPRESSION TESTER OR A CODE READER TO SEE IF ANY CODES ARE BEING STORED?
ALSO, DOES THE CAR HAVE A SECURITY LIGHT ON THE DASH?

Customer: replied 1 year ago.
WE HAVE A TESTER AND THEY TESTED IT AND ALL 4 READ 130 AND THERE IS NO SECURITY LIGHT ON THE DASH
Expert:  Mike V. replied 1 year ago.

Ok

if you unplug the crank sensor right now will the car start.

I need to know if the engine has ever been out of the car, or the transmission

also, the compression is a bit low, but it's not common for all cylinders to have precisely the same compression.

Does the car ever lose coolant and need to be topped off?

Customer: replied 1 year ago.
COOLANT IS FULL AND DON'T KNOW IF EITHER HAVE EVER BEEN OUT OF THE CAR, BUT THE CAR ONLY HAS 67K MILES AND LOOKS LIKE NEW. THE NISSAN DEALER SHIP SAID THAT IF YOU UNPLUG THE CRANK SENSOR THAT THE CAR WOULD START BUT WOULD NOT REV UP.
Expert:  Mike V. replied 1 year ago.

I understand they said that, I was just wondering if that was the case now or not.

I need you to check for spark, is that something you know how to do?

Customer: replied 1 year ago.
THEY ARE FIXING TO CHECK THAT NOW AND HOW DO YOU CHECK FOR SPARK?
Expert:  Mike V. replied 1 year ago.

Pull an ignition coil and leave it plugged in. Then set it next to something metal and crank the engine. If there is spark it will jump from the coil to the metal on the engine. Don't hold it or it will zap you, just set it next to a bolt and you should see spark jump from the coil to the bolt while cranking.

Customer: replied 1 year ago.
IT HAS VERY LIGHT SPARK WHEN PLUGGED IN AND WHEN WE UNPLUGGED THE CRANK SENSOR IT WOULD CRANK UP
Expert:  Mike V. replied 1 year ago.

Ok

I do not think the issue is the timing chain. Since it will start without the crank sensor plugged in, I think there is a problem with the signal wheel on the flywheel. I've seen this in the past on cars that have had the flywheel out or off and not installed correctly. Un plug the crank sensor and they start. Plug it back in and they don't. There is a problem with the ring on the fly wheel in my opinion. either it's loose or broken or it's been out and isn't installed properly.

I think the issue is there and the engine and transmission are going to have to be separated to find out what's going on in there.

Please let me know what more I can do to assist you today. Also, please remember to rate my answer, Just Answer does not compensate me for my time and resources. Follow up questions are included in the price of your question. If you are using the free trial, or have a subscription a rating is still required.
Thank you so much!

Customer: replied 1 year ago.
IS THERE ANY WAY TO SEE IF VISUALLY BEFORE WE HAVE TO TEAR IT APART (WE HAD THE CAR RUNNING IN THE SHOP CLEANING IT UP. THEN WE GOT IN THE CAR AND IT WOULD NOT START SO WE UNPLUGGED SENSORS AND CLEANED BATTERY TERMINALS, MOVED WIRES AROUND, GOT IN THE CAR AND IT WOULD CRANK RIGHT UP AND WE DROVE THE CAR OVER 200 MILES STOPPING AND STARTING SEVERAL TIMES TO THE AUCTION AND CAR SAT FOR 1 HOUR AND CAR STAARTED AND RUN GOOD ALL THE WAY BACK HOME AND THEN SAT OVERNIGHT AND WOULD NOT START AGAIN.) WE JUST HATE TO HAVE TO PULL EVERYTHING APART
Expert:  Mike V. replied 1 year ago.

Sorry for the delay.

I would not pull it apart, but man it sure sounds like the issue is there. But, it might be the wiring from the sensor. If you look at the wiring harness clear up to the computer, you might see where it's chaffed and there is a wire making contact.

Also, if you didn't put a factory crank sensor in the car, that could be the issue as well. From the sound of it though, it's got to be the wiring or the sensor ring. With this explanation though, I would not rip the engine out just yet. You can also try a wiggle test on the harness. Wiggle the wires while cranking the engine. If it starts, then perhaps you are actually getting a wire to make contact.

Customer: replied 1 year ago.
THE NISS Dealer did put a fact crank sensor and anew plug but we are going to check from their up tomorrow and go from their will call back then if that's ok thanks Randy,
Expert:  Mike V. replied 1 year ago.

That's fine, I should be online. I am really curious now! Seems like what you had done prior to this shouldn't be a factor if the wiring is good.

Customer: replied 1 year ago.
HEY MIKE WE ARE STILL WORKING ON THIS CAR, WE CHECKED WIRE CONNECTORS, GROUNDS, , FUSE BOX CONNECTIONS, TRIED TO CHECK CODES, WOULD NOT CONNECT, TRIED TO CRANK AGAIN WITH CRANK SENSOR DISCONNECTED NOW IT WILL NOT CRANK AT ALL, TRIED RECONNECTING STILL NO CRANK, PULLED OUT AND CLEANED HAD OIL ON CRANK SENSOR, CLEANED WITH CARB CLEANER AND SPRAYED IN HOLE TO TRY TO CLEAN RING, PUT BACK IN AND TRIED AGAIN STILL NO CRANK, SWAPPED NEW COMPUTER OUT WITH OLD COMPUTER THEN IT STARTED READING CODES, AND IT SAYS AIR TEMP SENSOR AND POWER STEERING PRESSURE SENSOR TRIED TO CRANK AGAIN STILL NO CRANK SWAPPED COMPUTER OUT AGAIN WITH THE NEW COMPUTER AND NOW IT READS CODES BUT IT STILL WILL NOT CRANK. BAFFLED!!!
Expert:  Mike V. replied 1 year ago.

Check the wiring harness where it runs under the battery in the left front corner of the car. Starting to think there may be an issue to the ecm relay. This used to happen on the older models.

Customer: replied 1 year ago.
OK GOING TO CHECK THAT NOW
Expert:  Mike V. replied 1 year ago.

I find it odd that the computer will read at times and not at others. In the older models once in a while the power feed to the ecm relay would fail and the car wouldn't start. So, I am wondering if it's something like that, and when the car won't start it's because the computer will not power up

Customer: replied 1 year ago.
SORRY FOR TAKING SO LONG TO GET BACK WITH YOU WE ARE STILL WORKING ON THAT NISSAN, WE HAVE STRIPPED ALL THE WIRES CHECKED ALL WIRES POSSIBLE FOR ANY BREAKS OR PROBLEMS SWAPPED COMPUTER AGAIN PULLED CRANK SENSOR AND CLEANED AGAIN TRIED TO START WITH CRANK SENSOR PLUGGED IN AND UNPLUGGED STILL NO START. PULLED VALVE COVER TO CHECK TIMING COULD NOT FIND TIMING MARKS ON CHAIN, BUT READ THAT #1 CYLINDER WAS TDC AND CAMS WERE POINTING STRAIGHT OUT AWAY FROM EACH OTHER TIMING WOULD BE RIGHT AND THAT IS THE WAY THEY ARE. DO NOT KNOW WHAT THE NEXT STEP IS THANKS
Expert:  Mike V. replied 1 year ago.

You are going to have to pull this engine and look at the flywheel. It's had to have been off the car or something for this to be going on. Otherwise I really have no answer as to what could be the problem. Maybe some sort of water intrusion, but honestly that seems unlikely. Since it will start and run with the crank sensor unplugged, it's got to either be an issue with the wiring for the crank sensor itself or something with the fly wheel in my opinion. You have eliminated everything else.

Customer: replied 1 year ago.
IT WILL NOT CRANK WITH THE CRANK SENSOR PLUGGED IN OR NOT NOW. CAN THE VARIBLE TIMING VALVE HAVE ANYTHING TO DO WITH IT OR IS THERE ANY TEST POINTS THAT WE CAN START AT TO ***** AND GOING TO THE COILS AND CHECKING VOLTAGE AND CRANK SENSOR
Expert:  Mike V. replied 1 year ago.

Ok

Just to be clear here, the engine cranks but doesn't start?

Customer: replied 1 year ago.
THAT IS RIGHT
Expert:  Mike V. replied 1 year ago.

Ok,

Well, you have to start with the basics, check and make sure there is spark. If there isn't any, then check for power at the connector at the coils, if there is spark, then spray some stating fluid directly into the throttle and see if the engine will fire off it for a few seconds. If it won't, then check for injector pulse with a noid light. If no pulse, then check the fuel injectors for power.

Also, if the battery is weak and the engine isn't cranking over fast enough, the computer won't come on and start the car.

If you have been cranking the car and it's not starting, the cylinders could be washed and that will give it low compression. This will prevent it from starting.

Try these tests in the order I have given you and let me know what you find when you are done.

Expert:  Mike V. replied 1 year ago.

and please, turn off your caps lock ;)

Customer: replied 1 year ago.
If we put a scope light in the crank sensor hole, would we be able to tell anything by that, next as far as spark, there is one weak spark at first crank, then no other tried to spray it there was still no spark do have 12 volts of power at coils.
Expert:  Mike V. replied 1 year ago.

Ok

the computer is suppose to tell the coils for fire. It does this via the cam and crank sensor positions.

Can you please tell me the position of the crank sensor on the engine so I know you are looking at or unplugging the right sensor here?

Customer: replied 1 year ago.
It is the sensor and the wire that the Nissan dealership replaced on the back side of the motor close to the motor mount. That was the first thing that Nissan tried they said the sensor and the pigtail was bad so they replaced it.
Expert:  Mike V. replied 1 year ago.

Ok

It's the right one, if I had a dollar for the wrong sensor being replaced we would not be chatting here.

It seems like maybe their connection on the new pigtail could be to blame. If you have a scan tool that can see the engine rpms, hook it up and see if it sees the engine cranking and gives you any rpms. It should also show the timing degrees.

Let me know.

Customer: replied 1 year ago.
We do not have one of those tools is there another way to check
Expert:  Mike V. replied 1 year ago.

Not really, at this point we have to see what the computer is seeing and why it's not telling the coils to fire.

I would look under the dash for any signs of some kind of aftermarket security system on the car at this point. I am not sure what else can be done without proper testing equipment.

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